Siem Reap — "Defeat of Siam" — is the gateway to the greatest concentration of medieval monuments on earth. Angkor Wat, Angkor Thom, Ta Prohm, Preah Khan, and a hundred other temples spread across the Angkor Archaeological Park are the reason most people come, and three days is the practical minimum to see the essentials. The city itself is small and walkable, sitting on the Siem Reap River between a canal and the southern edge of the park.
Beyond the temples, the huge natural reservoir of Tonlé Sap lies to the south. A boat trip to Kampong Phluk or other floating villages on the lake is one of the most memorable half-day excursions in the country. The Cambodia Landmine Museum on the road to Banteay Srei is harrowing but essential; run by former Khmer Rouge child soldier and self-taught deminer Aki Ra, it gives context to a landscape that is still being cleared of ordnance.
In the evenings, Phare, the Cambodian Circus puts on one of the best performances in Southeast Asia — a social-enterprise troupe combining acrobatics, music, and storytelling. Pub Street and the Old Market quarter provide the standard nightlife and souvenir options; the Wat Damnak and Wat Bo neighbourhoods east of the river are quieter and have better restaurants, including the remarkable Cuisine Wat Damnak.
The Angkor National Museum on Sihanouk Avenue is worth an hour before or after the temples for context on Khmer history. Hire a tuk-tuk driver through your hotel for the Angkor circuits — most are knowledgeable and the relationship across multiple days is worth establishing early.